A STUDY OF THE RELATIONS OF AFFERENT IMPULSES 
TO THE ACTIVITY OF THE CENTRAL CARDIO¬ 
VASCULAR NERVOUS MECHANISM 


BY 


JOSEPH TULGAN 

From the Department of Physiology of Columbia University, New York 




Submitted in partial fulfillment of the requirements for the degree of Doctor of 
Philosophy in the Faculty of Pure Science, Columbia University 


Reprinted prom The American Journal of Physiology, 
Volume LXV, Pages 174-199, June, 1923. 
Baltimore, Maryland 



















































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Reprinted from The American Journal of Physiology 
Vol. 65, No. 1, June, 1923 


A STUDY OF THE RELATION OF AFFERENT IMPULSES TO 
THE ACTIVITY OF THE CENTRAL CARDIO-VASCULAR 
NERVOUS MECHANISM 

JOSEPH TULGAN 

From the Department of Physiology, Columbia University, New York 
Received for publication March 5, 1923 

Experiment shows that there is a clear relationship between impulses 
arising from experimental stimulation over specific afferent nerves 
and changes in heart rate and blood pressure. The question arises 
whether the maintenance of a certain degree of activity of the heart 
and blood vessels, as manifested by the maintenance of blood pressure, 
is dependent upon afferent impulses in any degree or wholly independent 
of them. In other words, is the maintenance of blood pressure a reflex 
or an automatic function? 

There is no method previously employed for eliminating the afferent 
pathway from the heart to the central nervous system while leaving the 
efferent path intact. It is possible, however, to leave the afferent path 
intact and eliminate temporarily a part of the efferent pathway through 
the action of such drugs as atropine. 

One may divide one or both of the vagi anatomically and note the 
changes in heart rate, or one may eliminate the efferent fibers of the 
vagi by the administration of atropine, leaving the afferent fibers intact, 
but neither method really gives any clear answer to the question whether 
the action of the vagus under normal conditions is reflex or automatic. 
The problem is further complicated by the presence of the accelerator 
fibers, and the effect of the elimination of the vagi may conceivably 
differ according to whether the accelerators have or have not previously 
been divided. There are, then, several possible conditions under which 
the effect of elimination of the cardiac nerves may be studied. 

Anatomical. 1 . Division of both vagi, with the accelerators intact. 
This would include depressor fibers in some animals, but not in the 
rabbit. 

2. Division of both vagi after previous removal of the stellate ganglia. 

3. Atropine, vagi intact and accelerators intact. 

174 

Gift 

aiveraH* 

JUN 25 1923 





AFFERENT IMPULSES AND CARDIO-VASCULAR CENTERS 


175 


4. Atropine, vagi intact but with previous removal of the stellate 
ganglia. 

5. Section of accelerators, vagi intact. 

6. Section of accelerators after division of both vagi. 

7. Section of accelerators after administration of atropine. 

The observance of all these conditions becomes necessary because of 
the possibility that the action of the accelerators may be related to 
afferent impulses over the vagus, since the existence of other true afferent 
cardiac nerves is doubtful. If afferent cardiac fibers do run in the 
accelerators, more conditions are introduced, all of which demand 
analysis. And to the various procedures given above, we must add 
division of the dorsal roots of the spinal nerves. 

It may be remarked in passing that no complete experimental analysis 
of the problem has yet been made. And by the same token no clear 
answer can as yet be given to the question of the functional relation of 
afferent to efferent roots in the cardio-vascular system. 

Just as it was necessary to inquire into the relations of afferent to 
efferent roots in the matter of the nervous control of the skeletal 
muscles in order to decide which of their responses were reflex and which 
automatic in nature, so we must go over the relation of afferent roots 
to efferent roots in the study of the cardio-vascular reactions. For 
purposes of simplicity and convenience in handling, we may consider 
separately the cardiac and vascular reactions, and then later try to get 
at the reciprocal reactions of the two parts of the same mechanism. 

It has been shown that stimulation of the central end of the vagus, 
when one is divided and the other intact, slows the heart as a rule, 
although there is occasional acceleration of the heart instead. It has 
been shown also that the vagus is the only afferent nerve stimulation of 
which will consistently slow the heart. There are both afferent and 
efferent fibers in the vagus and it has been impossible up to the present 
to separate these anatomically. The determination of the relation of 
one set of fibers to the activity of the other must be arrived at by some 
other more round-about and possibly less certain method. 

The usual effect of section of both vagi is an increase in the rate of the 
heart and a rise of blood pressure. This simple experiment does not, 
however, throw much light on the question of whether the normal action 
of the vagus in keeping the heart rate down is reflex or automatic in 
character. In order to determine this point, further experimentation is 
necessary. It becomes necessary, therefore, to observe the conduct 
of the heart when the vagus is severed under a number of different 
conditions, which have been stated above. 


176 


JOSEPH TULGAN 


Statement of problem. Sherrington (1) has considered a funda 
mental characteristic of the responses of the central nervous system 
under the caption of the relation of afferent to efferent roots. The 
greater volume of work on this relationship has been devoted to the 
conditions prevailing in the somatic rather than in the visceral sensory 
and motor systems. While the responses of the somatic system are 
necessary for locomotion and other activities, and certain reactions of the 
organism to some conditions or changes of conditions in the external 
environment, the responses of the visceral system are necessary for the 
maintenance of the constancy of the internal conditions of the higher 
organism, such as systemic blood pressure, as well as for the adjustment 
of internal conditions in relation to the changes of the external conditions. 
The question arises whether the responses of the visceral system involve 
this relationship of afferent to efferent roots to the same degree as the 
somatic systems. 

Sherrington considers this question to some extent in his chapter 
(loc. cit.) but the degree to which this relationship holds in such a nervous 
mechanism as that for the control of respiration or blood pressure is not 
answered. Nor does one find this answer in any of the papers so far 
published. It is evident that for the proper understanding of the func¬ 
tion and manner of action of any of these visceral systems, the ascertain¬ 
ment of the degree to which the relation of afferent to efferent roots 
holds is a necessary preliminary. 

It may be pointed out here that just as the changes of internal 
conditions, practically independent of afferent impulses, may affect the 
respiratory rate, so it is possible that changes of internal conditions 
which are not primarily related to afferent nervous impulses may affect 
cardio-vascular activity. The relation of afferent to efferent roots may 
then be masked or modified by other internal conditions in the case of 
both of these systems, and the answer to our question may at first 
involve the indirect quantitative estimation of a number of factors in an 
equation rather than the direct determination of one of them. 

Historical. Beginning with the discovery by the Weber brothers 
of inhibition of the heart by applying one electrode to the spinal cord 
at the level of the 4th or 6th vertebra and the other to the nostril of a 
frog, and the later discovery of an inhibitory center by the same workers 
and others, the question as to whether this center and the vagi could be 
affected reflexly or not has been very much under discussion. Even 
after the vagus center had been definitely and minutely located in the 
medulla, very little progress had been made in regard to this question. 


AFFERENT IMPULSES AND CARDIO-VASCULAR CENTERS 177 

As a result, the mechanism of the nervous control of the entire cardio¬ 
vascular system was more or less in the dark. 

That the vagus center may be reflexly stimulated by stimulation of 
various afferent nerves, and that vagal tone may be altered by the blood 
itself has been shown. That psychical and emotional states could 
change vagal tone was also shown by many workers. By stimulation 
of the cerebrum itself marked changes in the pulse rate may occur. 
But all this work did not show whether the tone maintained by the vagus 
center is kept up reflexly by constant instreamings of afferent impulses, 
or whether the center had the power of automatism. These experi¬ 
ments do not, for instance, indicate what effects changes in the internal 
environment of the organism may produce on the center. 

That changes in the internal environment of an organism may have 
profound effects on pulse rate and blood pressure of an animal is very 
clearly shown by the changes in heart rate which follow deep inspiration 
and deep expiration. At the end of deep inspiration a marked increase 
in heart rate is observed as well as a marked increase in arterial tension; 
while a marked decrease in heart rate and a fall of arterial tension is 
observed at the close of deep expiration. The effect of any increased 
muscular work will change the internal environment to a certain degree, 
and this change may be accompanied by very great changes in the 
cardio-vascular system. This phase of the question has been largely 
overlooked by previous workers as well as by those who, until lately, 
have been working on the nervous mechanism of respiration. That 
vagal tone is maintained reflexly has been shown by some workers, such 
as Soltman, but the evidence presented by them is neither very clear 
nor very conclusive. In a similar manner evidence has been presented 
against this view which also lacks in conclusiveness. There is the work 
of Hill who makes the supposition that the terminations of the afferent 
nerves on the inner wall of the heart may be stimulated by intracardiac 
pressure and thus control the centers of circulation. That this view is 
perfectly tenable can be shown by the experiments of Johanssen (2) 
and many others who, after section of all the cardiac nerves, observed 
a rise of arterial tension and an increased heart rate on compression of 
the abdominal aorta. In the absence of the afferent pathways no 
stimulation arising from pressure in the heart can be effective reflexly. 
If however all the cardiac nerves are intact, Marey (3) noted that the 
compression of the abdominal aorta is followed by a decreased heart rate. 
Whether the central mechanism of the vagi is in this case affected by 
afferent impulses or by the increased intracranial pressure cannot be 


THE AMERICAN JOURNAL OP PHYSIOLOGY, VOL. 65, NO. 1 


178 


JOSEPH TULGAN 


determined. The heart, through the depressor nerves, has afferent 
connections with the central mechanism and by this means it is per¬ 
fectly possible for it to control reflexly its own rate. 

Sherrington (4) has sectioned all the dorsal roots of an animal in 
which he was recording blood pressure without getting any appreciable 
change in pressure. This fact seems to demonstrate that the vagus 
center is not dependent on afferent impulses coming in over the dorsal 
root fibers since, when all the afferent impulses, except those over the 
vagi, had been prevented from reaching it, there was little change in 
blood pressure. 

Stewart, Guthrie, Burns and Pike (5) have shown that after a total 
loss of function of the cerebral centers resulting from the temporary 
ligation of the head arteries there is a gradual return of function following 
the restoration of the circulation and that this return occurs in a fairly 
definite order. In a second publication, Stewart and Pike (6) reported 
a more detailed study of the time relations of the resuscitation processes 
in the most important of the bulbar centers, namely, the respiratory, 
vasomotor and cardio-inhibitor. Since by the production of complete 
cerebral anemia all the reflexes of the anemic region are temporarily 
abolished, advantage was taken of the opportunity afforded for the 
study of the relation between the return of such functions as respiration, 
or cardiac inhibition, and the opening up of the reflex pathways to or 
through their centers. In regard to the respiratory mechanism these 
authors found it was, of the three, the most automatic and the least 
dependent upon reflex stimulation for the origination of its discharge. 
The cardio-inhibitory center was the least automatic and is the most 
dependent upon such impulses while the vasomotor mechanism occupied 
an intermediary position between the other two mechanisms. The 
cardio-inhibitory center regains its power of being affected by reflex 
stimuli sooner than it does its tone. 

Stewart (7) has also shown that in dogs the rate of the heart when 
isolated from its extrinsic nerves by cerebral anemia is relatively con¬ 
stant when the external conditions (temperature and pressure of the 
blood) are kept constant. 

The r61e played by the accelerators is of course extremely important 
in a consideration of the cardio-vascular system. That they are 
purely efferent nerves has been generally believed, but whether they 
are dependent on afferent impulses or whether they work automatically 
has not been definitely determined. Tschirjew, Strieker and Wagner 
have witnessed, after section of the vagi, a decreased pulse rate on 


AFFERENT IMPULSES AND CARDIOVASCULAR CENTERS 


179 


excision of the inferior cervical and the first thoracic ganglia. It is 
also claimed that after section of the accelerators, inhibition by excita¬ 
tion of the vagus can be induced with great ease. Timofeew has kept 
animals for some time after section of the accelerators and noticed 
in them a gradual decrease in pulse rate. This fact evidently points to 
a tonic action maintained by the accelerators but it is held in check by 
the greater tonicity of the vagus center. It affords evidence also that 
the accelerators hold the vagus mechanism in check. 

Hunt and others have suggested that the tone maintained by the 
accelerator nerves is on blood pressure, since extirpation of the ac¬ 
celerators or the stellate ganglia is followed by a fall in blood pressure, 
in some cases amounting to 50 per cent. 

The question as to whether reflex cardiac acceleration may occur 
independent of the cardio-inhibitory center is one which has been fairly 
well investigated but on which there still exist many contradictory 
statements. There are two possible conditions under which reflex 
cardiac acceleration may occur: 1 , through a depression of the vagus 
action; or 2 , through a stimulation of the accelerator center. A great 
many investigators seem to favor the former view. Roy and Adami 
(8) conclude that the acceleration of the mammalian heart may occur 
only through the vagus center. Hunt confirms this view. 

In opposition to this view are those who maintain that a reflex cardiac 
acceleration may occur independent of the cardio-inhibitory center. 
Among these are Francois-Franck (9) who states that although the vagus 
center predominates over accelerator action under normal circumstances 
yet the reverse may be true under experimental conditions. Von Cyon 
(10) and Bayliss (11) also accept the view that reflex cardiac accelera¬ 
tion may take place through a stimulation of the accelerator center. 
The latter author has stimulated the depressor after section of both vagi 
and obtained an accelerated heart. Hering (12) observed in rabbits 
in which the last cervical and first thoracic sympathetic ganglia had 
been extirpated, that cardiac acceleration following muscular exercise 
was very much more reduced after than before the operation. That the 
second view is more tenable has also been confirmed by Hooker (13). 

Gasser and Meek (14) claim that the acceleration of the heart at the 
beginning of voluntary exercise in the normal animal is chiefly due to 
the decrease in the tone of the cardio-inhibitory center. Their work 
leads them to believe that the accelerators are a factor of safety and 
that, in exercise, their action is superimposed on that of the vagi only in 
times of great need. Aside from this these authors claim that their 
chief function is to maintain the level of the resting pulse. 


180 


• JOSEPH TULGAN 


Experimental procedure. All the experiments were done on cats. 
The laboratory procedure was ether anesthesia and tracheotomy. Blood 
pressure was recorded by means of a mercury manometer connected to 
the left carotid artery. Records were made on a Hurthle kymograph. 
The time was recorded in seconds by a Jacquet chronograph. A signal 
magnet served as the base line for blood pressure. At all times a suffi¬ 
cient amount of ether was given to abolish all sense of pain in the animals 
experimented on. The depth of anesthesia was judged by the presence 
or absence of the corneal reflex. The heart rate was computed in 
beats per minute. In every case a control tracing of blood pressure and 
heart rate was taken before any other procedure was attempted. 

Atropine was administered either directly intravenously or indirectly 
by stomach tube. In the former case the femoral vein was dissected out 
and a cannula was inserted into it. Atropine was injected by means of a 
hypodermic syringe, the needle of which was plunged into a rubber tube 
attached to the cannula. Backflow was prevented by a clamp on the 
free end of the rubber tube. In the latter case, a rubber tube was 
inserted into the esophagus until it reached the stomach. The drug was 
injected by plunging a hypodermic needle directly into the rubber tube. 

The solution of atropine was made up by weighing out a definite 
amount of atropine sulphate and dissolving it in a definite amount of 
one-seventh molecular solution of sodium chloride. In this way it was 
known how many milligrams each cubic centimeter of solution con¬ 
tained, and the dose was injected accordingly. The solution kept very 
well in a stoppered bottle at room temperature for several days. The 
dose injected was about 2 mgm. contained in 1 cc. of saline solution. 
This amount was, however, not strictly adhered to, since the animals 
varied from half-grown to full-grown cats. 

I. Division of both vagi with the accelerators intact. In 
animals such as the rabbit in which the depressor fibers of the vagus of 
most individuals run in a separate strand, the effect of the division of the 
vagi may be observed independently of the effect of the section of the 
depressor fibers. In the cat and the dog, this separation of the two kinds 
of fibers cannot be made so easily. As has been indicated, section of the 
vagi may be done with or without the concomitant division of the de¬ 
pressor according as the rabbit or some other mammal is used for the 
experiment. In cats, which were used throughout these experiments, 
bilateral vagotomy is followed usually by an increase of heart rate and 
blood pressure. The effect varies somewhat with the general systemic 
blood pressure at the time the section is made and with the general 


AFFERENT IMPULSES AND CARDIO-YASCULAR CENTERS 


181 


depth of anesthesia. If for any reason the heart rate is abnormally 
high, there is no increase on division of the vagi. 

In some of the cats used, separate depressor fibers were found, but the 
number was so small that even in those animals in which the separate 
depressor fibers were found the section included these fibers. It 
might be added here that very often a great deal more trouble was 
encountered in animals with separate depressor nerves than in those in 
which these fibers run in the vagus. Not only was this my experience 
but also that of Doctor Coombs who was doing experiments in this 
laboratory at the time this work was in progress. 

Both vagi, after being carefully dissected out, were exposed for a 
distance of about 2 cm. and then loose ligatures were passed around them. 
The section of both nerves was made practically simultaneously. The 
results of double vagotomy are found in the table below, which gives 
an average of about fifteen such experiments. 


TABLE 1 



RATE 

PRESSURE 

Before division of both vagi. 

212 

136 

After division of both vagi. 

229 

151 

Percentage change. 

8 

11 


In practically every case studied, bilateral vagotomy was followed 
immediately by a rise of systemic pressure and an increased heart rate. 
In some instances the rise in pressure was preceded by a slight fall 
which was probably due to a stimulation of the efferent fibers of the 
nerves during the process of lifting them or by the very act of cutting 
them. This initial fall was very slight, however, and was immediately 
followed by the usual rise. It will be observed on consulting the table 
that there is a change both in heart rate and blood pressure. 

In some animals section of both vagi was frequently followed by a 
great impairment of respiration. The animals had great difficulty in 
respiration, and very often artificial respiration had to be given for sev¬ 
eral minutes. In some animals the blood pressure fluctuated greatly for 
some time after bilateral vagotomy, but after a short time the usual 
rise in pressure and acceleration of the heart was obtained, and this 
was maintained fairly uniformly until the end of the experiment. 

II. Division of both vagi after previous removal of the 
stellate ganglia. The method used in the dissection for the stellate 











182 


JOSEPH TULGAN 


ganglia was suggested by Professor Pike. It is safer than any of the 
other methods tried since the chances of puncturing the pleura and 
producing a pneumothorax are much lessened by this method. 

The pectoralis muscles were dissected away. The initial incision was 
made in the midline of the sternum, thus avoiding most of the large 
blood vessels. After this dissection, the ribs and the intercostal muscles 
were exposed. The next group of muscle to be dissected away was the 
chief muscles of the neck which included the cleidomastoid, sternohyoid, 
sternomastoideus, sternothyroideus and the scalenus. The trachea 
and the esophagus were thus exposed. With a pair of pointed forceps 
around which a small piece of cotton was wound, the highway of the 
esophagus was followed until a point where merely moving the esophagus 
slightly aside revealed the inside of the thorax. The stellate ganglia 
lie between the first and second ribs, and merely pushing the muscles 
aside reveals them. With a fine pair of pointed forceps the ganglion 
was raised and then removed with a fine pair of scissors. 

Removal of both stellate ganglia is immediately followed by a con¬ 
siderable fall of blood pressure, at times more than 50 per cent. The 
heart rate slows and neither pressure nor rate increases. If both vagi 
are sectioned following the removal of the stellates there is a gradual 
rise of blood pressure which, however, never reaches the pressure which 
was maintained before the stellate ganglia were removed. There is also 
a striking increase in heart rate. It would seem as if section of the vagi 
allows the heart to escape from the tone which these nerves maintain 
over it. However, the rate which was maintained at the beginning of 
the experiment is never regained, as reference to table 2 will show. 

It will be seen, therefore, that the removal of the stellate ganglia is 
followed by an immediate large fall in pressure, to a level which is 
maintained throughout the experiment provided no other lesions are 
made. The heart rate also decreases and this decrease is constant under 
the same conditions. But if bilateral vagotomy is now done, the pres¬ 
sure goes up somewhat but never reaches the normal level. The same 
is true also of the heart rate. In other words, it would seem as if blood 
pressure and heart rate are maintained by the stellate ganglia and the 
accelerator nerves while the vagi are concerned with keeping up a slight 
tonic action on blood pressure, but that their main function is to keep 
the rate of the heart down so that it is not overworked. 

Hunt (15) has shown that the maintenance of a certain degree of 
blood pressure seems in some way to be connected with the stellate 
ganglia as is shown by what happens when they are removed, for then 


AFFERENT IMPULSES AND CARDIO-VASCULAR CENTERS 


183 


both the rate and the pressure fall. Wickwire (16) has shown that the 
removal of the accelerators alone results in a moderate decrease in 
heart rate and a great fall in pressure. 

Reference to the following table will bring out the points mentioned 
above more clearly. 

III. Atropine: Vagi and accelerators intact. Atropine is an 
alkaloid which paralyzes the terminations of a number of nerves, more 
especially of those of autonomic, as distinguished from sympathetic, 
origin that supply the involuntary muscles, secretory glands and the 
heart. By virtue of this property, it paralyzes the inhibitory termina¬ 
tions of the vagus in the heart and stimulation of this nerve therefore 
causes no change or at least, no decrease of the pulse after its adminis¬ 
tration (17). Small quantities of atropine have no further action on the 
heart than the paralysis of the inhibitory nerve endings. The termina¬ 
tions of the accelerator nerve endings are not affected. The heart 


TABLE 2 



RATE 

PRESSURE 

Before removal of stellate ganglia. 

173 

147 

After removal of stellate ganglia. 

149 

92 

After division of both vagi. 

160 

105 

Percentage change when the stellate ganglia are re¬ 
moved first. 

8 

29 



therefore after the administration of this drug is in a position as if the 
efferent fibers of the vagi had been cut in the neck. This results in a 
marked quickening of the heart. 

In these experiments atropine was at first injected intravenously. 
In each case the heart was markedly accelerated. At the beginning 
there was always a decreased pressure which is probably due to the 
action of the drug on the heart musculature itself. In later experiments 
atropine was given by stomach tube so that its absorption into the blood 
stream was much slower than when given directly intravenously. In 
such cases besides getting the acceleration of the heart, a slight rise of 
blood pressure was also obtained. In other words, administration of 
atropine in small quantities into the blood stream has the same effect 
as bilateral vagotomy except that the afferent pathway of the vagi is 
open. Table 3 will show this fact more clearly. 

Schiff (18) about fifty years ago maintained that stimulation of the 
peripheral end of the vagus nerve after atropine had been administered, 











184 


JOSEPH TULGAN 


always resulted in an increased heart rate. In other words, he showed 
that the vagus contains accelerator fibers and that after atropine was 
injected the inhibitory fibers were paralyzed while the accelerator fibers 
were not acted upon, so that stimulation of the peripheral end of the cut 
vagus resulted in a stimulation of the accelerator fibers with the result 
that the heart rate was acclerated. Arloing (19) also maintained that 
there were accelerator fibers in the mammalian vagus. I repeated this 
experiment and obtained the same results. In every case, practically, 
stimulation of the peripheral end of the cut vagus after atropine had 
been administered gave an increased heart rate. 

Another point of interest which was brought out in these experiments 
is the fact that the accelerators are receiving afferent impulses from the 
vagi and that therefore there is a definite relationship between afferent 


TABLE 3 



RATE 

PRESSURE 

When injected intravenously: 



Before injection of atropine. 

183 

145 

After injection of atropine. 

195 

122-106-97-92-83 

When injected by stomach tube: 



Before injection of atropine. 

210 

127 

After injection of atropine. 

216 

132 

Percentage change. 

3 

4 


to efferent roots in the maintenance of blood pressure. The following 
series of experiments will tend to bring this point out. 

Atropine was administered either directly intravenously or by the 
stomach tube, and sufficient time was given for its absorption and action. 

The vagus contains both afferent and efferent fibers but only the latter 
are affected, leaving the afferent pathway intact. After the lapse of a 
short time either the right or the left vagus was sectioned, and its central 
end ligated. A medium tetanizing current was then used to stimulate 
this central part of the nerve. If the stellate ganglia and the accelerator 
nerves were intact a rise of pressure was always obtained. If however 
the accelerators had been removed, this rise in pressure was never 
obtained, but a fall was the rule. In other words afferent impulses from 
the vagus nerves reflexly affect the central accelerator mechanism, so 
that this is in a measure dependent for its activity on the afferent im¬ 
pulses coming over the vagi. 














AFFERENT IMPULSES AND CARDIO-VASCULAR CENTERS 


185 


IV. Atropine: Vagi intact but with prior excision of the 
stellate ganglia. In this series of experiments excision of the stellate 
ganglia was immediately followed by a great fall of pressure and a 
decreased heart rate. After the administration of atropine, either 
intravenously or by the stomach tube, the blood pressure rose slightly 
while the heart rate also increased. Administration of atropine after 
the removal of both stellate ganglia gives results somewhat similar to 
those following bilateral vagotomy after excision of the stellate ganglia. 
This series of experiments again illustrates the fact that the maintenance 
of a certain degree of blood pressure is dependent upon the accelerators, 
while the vagi maintain a slight tonic action on blood pressure after the 
removal of the accelerators or the stellate ganglia. Likewise a tonic 
action is maintained by the vagi on heart rate, for after their section or 
paralysis by atropine the heart is immediately accelerated, although the 
rate maintained at the beginning of the experiment is never reached, if 


table 4 



RATE 

PRESSURE 

Before excision of the stellate ganglia. 

202 

152 

After excision of the stellate ganglia. 

184 

82 

After the injection of atropine. 

190 

115 

Percentage change. 

6 

24 


the vagi are sectioned or paralyzed by atropine subsequent to the 
excision of both stellates. 

Stimulation of the central end of the right or left vagus with the other 
one intact, and with atropine administered, but with the stellates 
removed, results in a fall of pressure, whereas with the stellates intact 
the usual rise of pressure is obtained. This again illustrates the fact 
that the central accelerator mechanism is in a measure dependent for 
its activity on the afferent impulses coming over the vagi. 

V. Section of accelerators, vagi intact. Section of the ac¬ 
celerator branches from the stellate ganglia results in a fall of pressure. 
The heart rate however does not seem to be reduced as much in this 
case as when the stellate ganglia are completely removed, in which case 
there is a great fall in pressure and heart rate. With the accelerator 
branches alone sectioned, the pressure subsequently goes up slightly 
and with it the heart rate is somewhat accelerated. This is possibly, 
even probably, due to accelerator impulses reaching the heart through 
the cervical ganglia (20), (21). 













186 


JOSEPH TULGAN 


VI. Section of accelerators after division of both vagi. 
Section of both vagi is followed by the usual train of events, namely, an 
accelerated heart and a rise of blood pressure. This increased heart 
rate and blood pressure is maintained if no other experimental lesions 
are made, but if the accelerators are sectioned subsequent to bilateral 
vagotomy there is a fall of pressure and a decreased heart rate. The 
fall of pressure due to section of the accelerators is not as great in this 
case as in the case where the stellate ganglia are first removed and 
double vagotomy done subsequently, but the change in heart rate in the 
first case is greater than in the second case. It would thus appear that 
the ultimate heart rate and the ultimate blood pressure depend con¬ 
siderably on whether the accelerators or the vagi are sectioned first. 


table 5 



BATE 

PRESSURE 

Before accelerators are sectioned. 

158 

147 

After accelerators are sectioned. 

156 

95 

Percentage change. 

2 

35 


TABLE 6 



RATE 

PRESSURE 

Before the division of both vagi. 

202 

138 

After the division of both vagi. 

218 

152 

After section of the accelerators. 

180 

105 

Percentage change. 

11 

24 



With the ultimate heart rate the opposite seems to be true, namely, 
there is a greater final fall in heart rate when the vagi are sectioned first 
and this procedure followed by section of the accelerators than when the 
accelerators are sectioned first and this procedure followed by double 
vagotomy. 

VII. Section of the accelerators after administration of 
atropine. In practically all respects this series of experiments agrees 
with the results that would be obtained if the vagi had been sectioned 
and this procedure followed by the removal of the accelerators. The 
percentage changes, however, were not quite as large. Upon the ad¬ 
ministration of atropine the blood pressure rose and the heart rate was 
increased. Now if the accelerators are removed, blood pressure falls 





















AFFERENT IMPULSES AND CARDIOVASCULAR CENTERS 


187 


while the heart rate decreases. It would seem that if the vagi are first 
paralyzed by atropine or sectioned, the subsequent removal of the ac¬ 
celerators is followed by a smaller fall of blood pressure and a slightly 
greater decrease in heart rate. Immediately upon the removal of the 
accelerators, the pressure falls; in time the pressure gradually rises, but 
the initial pressure and the heart rate are never reached again. 

It would thus appear that when all the extrinsic cardiac nerves are 
cut, either the heart rate falls somewhat and blood pressure considerably 
or there may be a greater decrease in heart rate and only a moderate 
fall of blood pressure. The final result seems to depend on whether the 
vagi or the accelerators are removed first. Table 7 will bring this point 
out clearly. 

VIII. Section of the vagi subsequent to ligation of the ad¬ 
renals. This series of experiments was undertaken for the purpose of 
seeing whether adrenalin played any part in the maintenance of blood 


table 7 



HATE 

PRESSURE 

Before the administration of atropine. 

210 

127 

After the administration of atropine. 

216 

132 

After the accelerators are removed. 

194 

105 

Percentage change. 

10 

20 



pressure under the conditions given. In every case that has yet been 
investigated, the action of adrenalin on muscle is identical with that 
produced by stimulation of the sympathetic nerve supply to that tissue 
(22). Since the accelerators belong to the sympathetic nervous system, 
it was thought that there might possibly be some relationship between 
their influence over blood pressure and the amount of adrenalin secreted. 
The usual procedure in dissecting out the adrenals was to make an 
incision in the mid dorso-ventral line near the region of the kidney, 
great care being taken not to injure the diaphragm. The fat and 
fascia around the adrenals were carefully dissected away leaving the 
gland free all around. The adrenal lumbar vein which carries away the 
secretion of the gland was tightly ligated and then to make doubly sure 
a ligature was passed around the entire gland thus shutting it off com¬ 
pletely from the vein. In no case was there a sufficiently large 
hemorrhage to cause any change in heart rate or blood pressure. 

Immediately after ligation of the adrenals there was a small fall in 
pressure in every one of the series of animals studied. 











188 


JOSEPH TULGAN 


The next procedure was to section both vagi. In these experiments 
it was desired to see whether or not the accelerators cut off from a supply 
of adrenalin were able to cause the usual increased blood pressure and 
the usual increased heart rate, which is obtained after double vagotomy 
under normal conditions. Immediately following double vagotomy an 
increased blood pressure was obtained which lasted for a few seconds 
only, and then the pressure began to fall. The heart rate was however 
slightly increased both after ligating the adrenals and after double 
vagotomy. 

IX. Partial cerebral anemia followed by the removal of the 

STELLATE GANGLIA AND SUBSEQUENT SECTION OF THE VAGI. When, for 
any reason, the volume of blood circulating through the brain in unit 
time is greatly reduced, there is a cardio-vascular reaction in a direction 
tending to restore the normal volume conditions in the brain. Blood 
pressure rises markedly, and one often finds a departure from the usual 


TABLE 8 



RATE 

PHESSUBE 

Before ligation of the adrenals. 

210 

154 

After ligation of the adrenals... 

226 

144 

Immediately after double vagotomy. 

160 

A few seconds after double vagotomy. 

231 

135 



relations expressed in Marey’s law, of a slower pulse rate with a high 
blood pressure. The vasoconstrictor part of the response has been 
studied by Winkin (26) and it seems desirable to get some further 
evidence upon the more strictly cardiac changes under conditions of 
reduced blood supply to the brain, and the role payed by the cardiac 
nerves in the response of the organism to such a change of internal 
conditions. 

A state of partial cerebral anemia was induced by the occlusion of 
the right carotid artery, and the right and left vertebral arteries, but 
allowing a small amount of collateral circulation. Ligation of these 
cerebral arteries and the production of a state of partial cerebral anemia 
is followed in some animals by a fall of arterial pressure instead of the 
usual rise of pressure. This response was observed in a number of 
animals in this series of experiments. This condition can be remedied by 
releasing one of the vertebrals, usually the left. In this series of experi¬ 
ments the stellate ganglia were removed before the production of partial 













AFFERENT IMPULSES AND CARDIO-VASCULAR CENTERS 


189 


cerebral anemia. The usual fall of blood pressure and heart rate was 
observed following the removal of the accelerator influences on the heart. 
Now when the cerebral arteries were occluded, with the exception of the 
collateral circulation mentioned above, the pressure rose while the heart 
rate slightly decreased. On releasing the carotid, the pressure fell to 
slightly below normal. The second occlusion was also followed by an 
increased blood pressure, but in this case the pressure did not rise as high 
as in the first occlusion, while the heart rate slightly diminished. The 
third occlusion and every occlusion following was accompanied by a 
gradual decrease in blood pressure and heart rate. 

Section of the vagi during the period of partial cerebral anemia is 
followed by a great increase in blood pressure and heart rate as com- 


TABLE 9 



RATE 

PRESSURE 

Normal. 

225 

130 

Stellates removed. 

169 

94 

1st occlusion . 

183 

155 

2nd nenliisinn . 

173 

141 

3rd occlusion. 

160 

132 

Vagi sectioned . 

203 

180 

Normal circulation restored. 

193 

133 

1st. nf'.fdiisirvn .... . 

198 

172 

2nd occlusion . 

198 

170 

Find iof t.hfi ftvpftrimfiTit. . 

188 

115 



pared with blood pressure and heart rate when the vagi were still intact. 
Especially was there an increase in heart rate as the table below will 
show. Occlusion of the cerebral arteries is now followed by a pressure 
and rate much greater than in the case when the vagi were intact. The 
second and subsequent occlusions result in a rise of pressure which is 
much greater than in the previous case when the vagi were intact. In 
the case of the heart there is also an increase over the rate present when 
the vagi were intact, but the rate is not as high as the rate observed at 
the beginning of the experiment. 

A higher rate of the heart at the beginning of the experiment, than 
is ever attained after section of the accelerators and the vagi, indicates a 
tonic action of the accelerators. This is not consistent with the results 
of Gasser and Meek who deny the tonicity of the accelerator nerves. 

















190 


JOSEPH TULGAN 


X. Partial cerebral anemia followed by section of the vagi, 
stellate ganglia intact. A condition of partial cerebral anemia was 
induced as described above, with all the cardiac nerves intact. The 
usual rise of pressure and the slightly decreased heart rate are observed. 
The primary decrease in heart rate is usually followed later on by an 
increased heart rate if the condition of partial cerebral anemia is allowed 
to remain without any further lesion. This later acceleration might be 
explained by the following. Schiff showed that the accelerator fibers 
of the vagus resist degenerative changes longer than the inhibitory 
fibers. Arloing (19), who repeated SchifFs work, says there are four 
kinds of fibers in the vagus, one kind being the accelerator fibers, and 
confirms Schiff’s work as to their greater resistance to degeneration. 
Other experiments have shown that the accelerator fibers retain their 
vitality longer after death of the animal than the inhibitory fibers. It is 
conceivable therefore that the accelerators are more resistant to anemia 
than the inhibitory fibers. Stewart, Guthrie, Burns and Pike (5) and 
Winkin (26) have also shown that there is a vasoconstriction in the 
splanchnic area during cerebral anemia. The rise in pressure and the 
accelerated heart may perhaps be attributed to the action of the vaso¬ 
constrictor mechanism and in part to the action of the accelerator 
fibers in the vagus. 

The results of sectioning the vagi during a condition of partial anemia 
depend on whether the accelerators are present or not. If the ac¬ 
celerators are present, the pressure rises very high on partial occlusion 
of the cerebral arteries. On releasing the head arteries, the pressure 
never falls below the control pressure maintained by the animal; whereas 
if the accelerators have been excised, the pressure does fall below the 
control level. If the vagi are sectioned when the accelerators are not 
present, and then the cerebral arteries are occluded, the pressure does 
not rise very high and following the release the pressure falls below the 
control level. The accelerator mechanism seems to stand in the way 
of a falling blood pressure and saves the cells from a deficiency in the 
amount of blood circulating to them. 

A contrast of the deportment of the heart when the vagi are sectioned 
during a state of partial cerebral anemia with the accelerator mech¬ 
anism intact and with the accelerator mechanism removed is shown by 
the results of the following two experiments. 


AFFERENT IMPULSES AND CARDIO-YASCULAR CENTERS 


191 


- 

BLOOD PRESSURE 

Normal. 

122 

Cerebral arteries partially occluded after section of the vagi with 
the accelerators intact. 

210 

Normal circulation restored. 

125 

Normal. 

130 

Cerebral arteries partially occluded after section of the vagi and 
removal of the acelerators. 

140 

Normal circulation restored. 

105 



Section of the vagi during a state of partial cerebral anemia with the 
accelerators intact is followed by a great increase both in blood pressure 
and the heart rate. On releasing the cartoid the pressure and heart rate 
fall to a little above that maintained at the beginning of the experiment. 

TABLE 10 



RATE 

PRESSURE 

Normal. 

197 

128 

After occlusion. 

191 

197 

Vagi sectioned. 

214 

207 

1st occlusion.. 

217 

207 

2nd occlusion. 

212 

206 

3rd occlusion. 

212 

207 

4th occlusion. 

210 

206 

Normal circulation restored. 

200 

135 




XI. Partial cerebral anemia followed by section of the vagi 

AND SUBSEOUENT REMOVAL OF THE STELLATE GANGLIA. In this Case, 
section of the vagi is followed by the increased pressure and heart rate 
described in the preceding table. Now if the stellates are removed the 
pressure falls very much below normal, while the heart rate also de¬ 
creases. If a state of partial cerebral anemia is now induced by 
occluding the cerebral arteries, leaving a slight collateral circulation by 
way of the left vertebral artery, the pressure increases, while the heart 
rate remains about the same. The second and subsequent occlusions 
raise the pressure to about the same degree as the first occlusion, and 
the heart rate remains constant. It would seem as if the removal of the 
stellate ganglia had removed the mechanism by means of which a high 
blood pressure can be obtained, when it is to the best interest of the 
organism to have a higher pressure than is present. The absence of 




























192 


JOSEPH TULGAN 


this mechanism may then be injurious to the best interest of the organ¬ 
ism when a high blood pressure and an accelerated heart rate are 
necessary. 

XII. Section of the vagi during complete cerebral anemia. In 
all the experiments previous to this, the vagi were sectioned either when 
the entire circulation was intact or during a state of partial cerebral 
anemia when a certain amount of collateral circulation to the head was 
still open. In each case a rise of blood pressure and an increased heart 
was observed. Whether this effect was due to central or peripheral 
forces could not be determined under these conditions, and so the same 
experiment was repeated with complete cerebral anemia. The cerebral 
anemia was considered complete when all voluntary and involuntary 
activities had ceased. When the hind limbs became quiet, and the 


table 11 



BATE 

PRESSURE 

Normal. 

184 

130 

After occlusion.. 

168 

154 

Vagi sectioned. 

206 

197 

1st occlusion. 

206 

196 

2nd occlusion. 

202 

195 

3rd occlusion. 

204 

197 

Stellates removed. 

184 

94 

1st occlusion. 

184 

122 

2nd occlusion. 

184 

122 

3rd occlusion. 

186 

122 



blood pressure began to fall, complete cerebral anemia was present. 
If the vagi are sectioned during complete cerebral anemia, there is 
absolutely no change in blood pressure or heart rate as compared to 
that present before the section was made. If a state of cerebral anemia 
however, is not present, as in the case when the circulation to the head 
is not interfered with at all, section of the vagi is followed by a rise of 
blood pressure and an increased heart rate. 

This experiment then shows that the rise in blood pressure and in¬ 
creased heart rate, which are observed on sectioning the vagi, are a 
central effect and are not due to any peripheral activity for when the 
entire brain is made functionless by depriving it of its normal blood 
supply, the reactions that normally occur when the blood supply to it is 
intact, such as an increased blood pressure and heart rate, are abolished. 

















AFFERENT IMPULSES AND CARDIO-VASCULAR CENTERS 


193 


Discussion of results. At the beginning of this paper it was stated 
that the object of these experiments was to determine whether there was 
any relation of afferent to efferent roots in the maintenance of blood 
pressure or whether this function was entirely automatic. The central 
respiratory nervous mechanism and the central cardio-vascular mech¬ 
anism function so nearly alike in this respect that it would be well to 
state here the views of Pike and Coombs (23) in regard to the nervous 
control of respiration. These authors in a brief summary of the 
organization of the nervous mechanism of respiration conclude as 
follows. “While it is undoubtedly true that the respiratory center may 
act automatically under conditions which preclude the effect of afferent 
impulses, it is our opinion that its normal activity is not wholly auto¬ 
matic but partly reflex.” In various publications the same authors 
have shown that afferent impulses reach the respiratory center in higher 
mammals from the lungs and the respiratory epithelium generally, parts 
of the alimentary epithelium, the pleura, the muscles of the thoracic 


TABLE 12 



RATE 

PRESSURE 

Normal. 

168 

150 

Complete cerebral anemia. 

160 

200 

Vagi sectioned. 

160 

200 


walls, the diaphragm and the abdominal muscles. If the vagi are sec¬ 
tioned the rate of respiration is slowed for the reason that afferent 
impulses coming over the vagi, which are normally summed with the 
carbon dioxide in the blood to produce an excitation of the cells in the 
medulla, are no longer present, and the excitation of the central cells 
is now dependent in large part upon the carbon dioxide only. If now 
the dorsal roots of the spinal nerves are sectioned, there is a further 
fall in the respiratory rate, due to a greater loss of afferent impulses to 
the central cells in the medulla. The cells in the medulla now become 
wholly dependent upon the carbon dioxide of the blood. 

Briefly stated, then, the respiratory center normally receives afferent 
impulses from certain sensory fields. If these afferent impulses are 
prevented from reaching the central cells in the medulla by sectioning 
the vagi and the dorsal roots of the spinal nerves, respiration does not 
cease but continues in a modified form. The same statement can be 
made in regard to the central cardio-vascular mechanism. If all the 











194 


JOfcEPH TULGAN 


cardiac nerves are sectioned, the blood pressure does not drop to zero, 
but it is maintained at a certain level which is not the same as in the same 
animal with the cardiac nerves intact. 

The nervous centers concerned with the regulation of the cardio¬ 
vascular mechanism are situated in the medulla and have a wide relation 
with afferent nerve fibers from all parts of the body including the heart 
itself. To the heart go efferent fibers which carry impulses from the 
central mechanism which increases or decreases its rate, and to the blood 
vessels go fibers which may change their caliber and thus change blood 
pressure. Sherrington and Wickwire have shown that section of all 
the dorsal spinal roots has no effect on blood pressure, and so we may 
concern ourselves with the changes brought about by sectioning the 
cardiac nerves themselves. 

The problem of the relation of afferent impulses to the activity of the 
central cardio-vascular nervous mechanism may be divided into two 
parts. 1 , The determination of whether or not blood pressure may 
persist after section of all the afferent nerves; and 2 , the character of 
the response to changes at the periphery. There is little doubt that the 
respiratory mechanism in the medulla may function in the absence of 
all afferent nervous impulses. But it is equally clear that under these 
conditions no modifications of the respiration can be brought about by 
peripheral changes which cannot affect the central mechanism directly 
or indirectly through the blood. It is possible, also, that blood pres¬ 
sure may be maintained in the absence of all afferent nervous impulses, 
but the absence in such a steady uniform condition of any characteristic 
modification such as changes in the rate of respiration, would mask any 
noticeable manifestations of the effect of elimination of the afferent 
nervous impulses. One would expect, however, a failure of the usual 
responses to peripheral changes. 

That a definite relation between afferent and efferent roots exists in 
the maintenance of blood pressure has been shown in an earlier part of 
this paper. If atropine is injected, thus paralyzing the efferent fibers 
of the vagi, and then th e central end of the cut vagus is stimulated, a 
definite rise of blood pressure is obtained if the stellate ganglia and the 
accelerator nerves are intact; but a fall of pressure is the rule if the 
latter are removed. In other words, afferent impulses over the vagi 
reflexly affect the central accelerator mechanism. 

That blood pressure does persist after section of all the afferent nerves 
has already been shown. In this respect the cardio-vascular system 
may be compared to the respiratory system, since respiration will go on 


AFFERENT IMPULSES AND CARDIO-VASCULAR CENTERS 


195 


even after all the afferent nerves are sectioned, but in each case we get a 
modified type of respiratory or cardio-vascular response. This in¬ 
dicates that a certain amount of automatism is present in both these 
systems, but does not preclude the presence of the relation of afferent 
to efferent roots also. 

As to the character of the responses at the periphery after the elimina¬ 
tion of the afferent cardiac nerves, experiments indicate that there is a 
failure of the usual responses at the periphery. If the cerebral arteries 
are partially occluded when the vagi are intact, we get a rise of pressure 
not very much above the normal pressure while the heart rate decreases 
somewhat. If now the vagi are sectioned and afferent impulses from the 
heart can no longer reach the central cells in the medulla, a state of 
partial cerebral anemia results in a great rise of blood pressure and an 
increased heart rate. Wickwire (16) in a study of the reciprocal reac¬ 
tions of the cardio-vascular system has shown that when the vagi are 
intact compression of the abdominal aorta is followed by a compensatory 
response of heart rate to changing blood pressure, the magnitude of the 
response varying with the depth of anesthesia. The carotid blood 
pressure increases while the heart rate decreases. If the same experi¬ 
ment is carried out under similar conditions but with bilateral vagotomy, 
the compensatory response of a lower heart rate to increased blood pres¬ 
sure remains, but the degree of compensation is much less than before 
division of these nerves. Yates (24) has also found that if the medulla 
is intact, stimulation of the brachial plexus results in a rise of blood 
pressure. If the medulla is eliminated by producing a state of cerebral 
anemia the stimulation of the brachial plexus produces no rise of blood 
pressure. It seems safe to conclude that the response at the periphery 
seems to depend on whether afferent impulses can reach the central 
cardio-vascular mechanism. If these afferent impulses are prevented 
from reaching the medulla by sectioning the afferent nerves or by the 
production of a state of cerebral anemia the usual response at the 
periphery changes or fails entirely. 

It will be observed on consulting table 1 that if the vagi are sectioned 
there is an appreciable change in both rate and blood pressure. If 
afferent impulses, however, can reach the central mechanism as in the 
case where atropine is injected, the change in rate and pressure is not so 
large as is shown by table 3. It would seem that afferent impulses 
from the heart over the vagi are necessary to keep the rate and pressure 
down to a normal level so that the cardio-vascular system is prevented 
from maintaining too high a rate and pressure. In the case where the 


196 


JOSEPH TULGAN 


vagi are sectioned after both stellates are removed we also notice a 
greater fall in both rate and pressure than when, instead of sectioning 
the vagi, atropine is injected. In the latter case the afferent path of the 
vagus is still open and as a result of afferent impulses reaching the 
medulla the rate and pressure do not fall as markedly as when afferent 
impulses are prevented from reaching the medulla. A comparison of 
tables 2 and 4 will bring this point out. 

Again, if the accelerators are sectioned after division of both vagi 
we find a greater fall in both heart rate and blood pressure than when the 
accelerators are removed after atropine is injected. This again seems 
to point to the conclusion that afferent impulses over the vagi tend to 
keep the central cells in the medulla in check and brings out the relation 
of afferent to efferent roots in the maintenance of blood pressure. A 
comparison of tables 6 and 7 will bring this point out. 

There is no evidence from these experiments tending t.o show that 
afferent impulses over the vagi tend to inhibit the accelerator mechanism 
after the administration of atropine. 

These experiments have also brought out some points on the function 
of the cardiac nerves. If the vagi are sectioned after the removal of the 
stellate ganglia, the heart rate and blood pressure increase considerably. 
The normal action of the vagus then is to maintain a tonic action over 
blood pressure and heart rate. This fact is brought out still more 
strikingly in later experiments. If the stellate ganglia are removed and 
then the cerebral arteries are partially occluded, with the vagus intact, 
a rise of pressure is obtained as well as an increase in heart rate. The 
second occlusion, however, results in a rise of pressure which is not as 
large as the first, while the heart rate also decreases. The third occlu¬ 
sion results in a rise of pressure which is still lower than in the second 
case, while the heart rate also decreases. Every occlusion after this 
one is followed by a still smaller rise of pressure and a decreased heart 
rate. These results indicate that the vagi are concerned with keeping 
the blood pressure and heart rate down to or sometimes below a level 
which is to the best interest of the organism. The vagi seem to stand 
in the way of a rising tide of pressure, and this obstruction may be to the 
disinterest of the organism. Haldane has pointed out that in the case 
of the respiratory system the vagi may sometimes act to the disinterest 
of the organism. The same statement may be made in the case of the 
cardio-vascular system for sometimes the vagi may stand in the way of a 
rising pressure when it is to the best interests of the organism to have a 
high pressure, as in cerebral anemia. 


AFFERENT IMPULSES AND CARDIOVASCULAR CENTERS 


197 


The results obtained on section of the vagi during a state of partial 
cerebral anemia seem to depend on whether the accelerators are intact 
or whether they have been previously excised. If the accelerators are 
intact, section of the vagi is followed by a very high blood pressure. 
When the normal circulation is restored, the pressure does not, in general, 
fall below the level maintained at the beginning of the experiment. If, 
however, the accelerators have been excised preliminary to section of 
the vagi, partial occlusion of the cerebral arteries results in a rise of 
pressure which is not very much above the pressure maintained at the 
beginning of the experiment. Upon restoring the normal circulation, 
the pressure falls very much below that maintained at the beginning of 
the experiment. These experiments seem to show that the accelerators 
are in some way concerned with the maintenance of blood pressure. 
That they respond to the emergency of a falling pressure is well shown, 
for in the case where the accelerators are intact the pressure does not 
fall below normal on restoring the normal circulation. In their absence, 
however, the pressure does fall below the pressure maintained at the 
beginning of the experiment when the cerebral circulation is restored. 

With the loss of the accelerator mechanism the cardio-vascular mech¬ 
anism loses an efficient protection against a falling pressure, which would 
act to the disinterest of the organism. An increased pressure is then 
due to the accelerator mechanism which works to the best interests of 
the organism. 

The responses of the cardio-vascular system seem to be guided by two 
antagonistic mechanisms, a cardio-inhibitory nervous mechanism and a 
cardio-accelerator nervous mechanism, both of which through the 
algebraic summation of their effects act in the best interests of the 
organism under ordinary conditions. The first mechanism is concerned 
with preventing the heart from overwork, and in giving the heart 
musculature a sufficient period of rest for its metabolic repair. The 
second mechanism is intimately concerned with the maintenance of a 
certain level of blood pressure which is to the best interests of the 
organism. 

Friedenthal (25) has shown that animals in which the cardiac nerves 
have been sectioned exhibit no discomfort when at rest, but are unable 
to undergo any considerable exertion. This illustrates the tone, 
accelerator as well as inhibitory, which these nerves maintain over the 
heart. 

The vagus, although the inhibitory nerve to the heart, has been shown 
in these experiments to contain accelerator fibers. If atropine is 


198 


JOSEPH TULGAN 


injected, the inhibitory fibers are paralyzed, whereas the accelerator 
fibers are not affected. If the peripheral end of the cut vagus is now 
stimulated, the heart rate is accelerated instead of being inhibited. The 
presence of these fibers in the vagus may also explain in part the increased 
heart rate which is obtained after a preliminary decrease when a state 
of partial cerebral anemia is brought about. This is due to a greater 
resistance of the accelerator fibers to anemia than the inhibitory fibers, 
hence they will retain their activity after the inhibitory fibers have been 
made functionless by anemia. 

In the experiments in which the adrenals had been ligated preliminary 
to section of the vagi, the usual result of section of the vagi under 
these conditions was first a small rise of blood pressure followed by a 
fall in each case. The heart rate was, however, slightly increased both 
after ligation of the adrenals and after double vagotomy. What this 
factor was which caused the accelerated heart after these procedures 
was not determined. 

I wish to express my sincere thanks to Professor Pike for the sugges¬ 
tion of this problem and for his keen interest shown while these experi¬ 
ments were going on. 


CONCLUSIONS 

1. While the cardio-vascular system may undoubtedly act auto¬ 
matically under conditions which preclude the effect of afferent impulses 
its normal activity and particularly its response to changing conditions 
in the organism is not wholly automatic but partly reflex. 

2. Afferent impulses over the vagi reflexly affect the central accel¬ 
erator nervous mechanism. 

3. When the cardiac nerves are sectioned, the ultimate heart rate and 
the ultimate blood pressure depend on whether the vagi or the accel¬ 
erators have been sectioned first. 

4. The accelerators respond to the emergency of a falling blood 
pressure. 

5. The accelerator nerves seem to maintain a tonic action over the 
heart. 

6. The accelerators seem in some way to be concerned with the 
maintenance of blood pressure. 

7. There is a cardio-inhibitory and a cardio-accelerator mechanism, 
both working, under normal conditions, to the best interests of the 
organism. 


AFFERENT IMPULSES AND CARDIOVASCULAR CENTERS 


199 


8. There are accelerator fibers in the vagus. 

9. Adrenalin seems to be concerned with the rise of blood pressure 
on section of the vagi under the conditions of these experiments. 

BIBLIOGRAPHY 

(1) Sherrington: Schafer’s Textbook of physiology, 1900, ii, 797. 

(2) Johanssen: Arch. f. Physiol., Leipzig, 1891, s. iii. 

(3) Marey: “La Circulation du Sang,” Paris, 1881, 334. 

(4) Sherrington: Schafer’s Textbook of physiology, 1900, ii, 869. 

(5) Stewart, Guthrie, Burns and Pike: Journ. Exper. Med., 1906, iii. 289 

(6) Stewart and Pike: This Journal, 1907, xix, 328. 

(7) Stewart: Ibid., xx, 407. 

(8) Roy and Ad ami: Phil. Trans, of the Royal Soc., London, 1892. 

(9) FRANgois-FRANCK : Travaux du laboratoire de Marey, 1878-9, 73. 

(10) Von Cyon: Arch. f. d. gesammt. Physiol., 1897, lxviii, 434. 

(11) Bayliss: Journ. Physiol., 1893, xiv, 303. 

(12) Hering: Arch. f. d. gesammt. Physiol., 1895, lx, 429. 

(13) Hooker: This Journal, 1908, xix, 417. 

(14) Gasser and Meek: Ibid., 1914, xxxiv, 4S. 

(15) Hunt: Journ. Exper. Med., 1897, ii, 2. 

(16) Wickwire: This Journal, 1920, liii, 355. 

(17) Cushny: Pharmacology and therapeutics, London, 1915. 

(18) Schiff: Arch. f. d. gesammt. Physiol., 1878, xviii, 172. 

(19) Arloing: Arch. d. physiol, nor. et pathol., 1896, viii, 5e., serie 75. 

(20) Ranson: Journ. Comp. Neurol., 1918, xx. 

(21) Spadolini: Arch. d. fisiol., 1916, xv, 70. 

(22) Elliot: Journ. Physiol., xxxii, 401. 

(23) Pike and Coombs: Science, 1922, lvi, 691. 

(24) Yates: This Journal, 1921, lvii, 68. 

(25) Friedenthal: Arch. f. Physiol., 1902, 142. 

126) Winkin: This Journal, 1922, lx, 1. 





CURRICULUM VITAE 


Joseph Tulgan, born November 24, 1896 New York City. Attended 
Public Schools from 1905-1912. Graduated from Stuyvesant High 
School, New York City February 1916. Entered the College of the 
City of New York February 1916 and graduated February 1920. 
A.B., degree. United States Army 1918-1919 stationed at Camp 
Gordon, Army Medical School, and the Surgeon General’s Office. 
Matriculated under the Faculty of Pure Science Columbia University 
February 1920, A.M., June 1921, Ph.D., June 1923. Fellow in the 
Department of Biology College of the City of New York 1920-1921, 
Tutor 1921-1923. Instructor in Physiology Columbia University 1923. 
Elected to Sigma Xi Columbia University chapter March 1923. 












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